The author has identified the following significant results. The ERTS-1 satellite imagery has facilitated a major advance in accurate mapping and better understanding of the African Rift valleys. A unified scheme of mapping of the whole rift system, from Malawi to Ethiopia, has been accomplished. The structures revealed by the imagery are discussed in the light of known ground truth for the northern half of the African Rift System. The ERTS-revealed structures confirm the likelihood of a drift of Arabia away from Africa and impose constraints on the drift vectors. Numerous features have been newly recognized from the imagery: the gently curvilinear plan of virtually all the African Rift valleys, the pervasive but not overriding degree of influence of Precambrian structures on rift faulting, the deep structural control of many rift volcanic centers, the occurrence of several unsuspected calderas both in the rifts and on the plateaus, and massive cauldron subsidence phenomena previously unknown to eastern Africa. Lithological mapping in eastern Africa can be greatly refined using the ERTS imagery, and new or revised subdivisions of the Precambrian appear possible and, in some places, necessary. Valleys excavated in the Ethiopian highlands by Pleistocene glaciers are newly recognized.